1. Field of the Invention
The present invention generally relates to an image processing device, an image processing method, and a recording medium, and particularly relates to an image processing device having a color material save mode, an image processing method having a color material save mode, and a recording medium storing an image processing program.
2. Description of the Related Art
Image output devices have been known that have a normal output mode for generating and outputting an image at a normal density and a color material save mode for outputting an image using less color material than would normally be used. The color material save mode is used when the image quality is not important, such as when checking the layout of an output image.
Recent application software has often been used to create color documents containing a mixture of characters, graphics, and images. Therefore, related art color printers use a density conversion method, a method of calculating a logical between a dithered image and a decimation pattern, a pulse modulation method, a method of controlling the amount of light for writing, or the like, in order to reduce color material consumption.
Since these methods reduce the image density of output images, the output images have lower quality than would be achieved in a normal output mode. However, there is a demand for maintaining readability of especially important character images even in a color material save mode.
To meet such a demand, a method is proposed that reduces the usage of a color material for printing an entire image by applying a decimation pattern to an image portion and by reducing the density inside the contours of characters while applying edge enhancement to the character portion. Although this method can save a color material to be used for forming an image, an additional control process is required, and hence the processing speed is undesirably reduced.
Japanese Patent Laid-Open Publication No. 2003-66781 (corresponding to U.S. Patent Application Publication No. 2003/0047099 A1), for example, discloses a color printer that has a color material saving conversion table for each object, such as a character portion and an image portion, and that saves a color material without reducing the processing speed of the printer.
Such a color printer that has a color material saving (toner saving) conversion table for each object, such as a character portion and an image portion, and that saves a color material without reducing the processing speed of the printer, however, does not perform any other process, such as an edge detection, for improving the readability of characters, and hence the readability of a character portion is reduced when usage of a color material is reduced.